Telephone switching systems such a PABXs and central offices provide specialized applications, such as automatic call distribution (ACD) which distributes incoming calls among agents. Such systems can be used for answering inquiries as to departure or arrival times of aircraft, to take reservations for theater, aircraft, trains, etc., to take telephone orders, etc.
In such systems, when a subscriber calls a telephone number, such as an 800 or 888 number, the telephone system routes the call to an idle agent within a hunt group of agents accessed by the number. All agents within the group are accessible by the same number, but the system determines which agent has been the "longest idle agent" and routes the call to that agent.
U.S. Pat. No. 5,515,428, issued May 7, 1996, invented by Mark Sestak and Paul Erb, and assigned to Mitel Corporation, describes prior art methods and a new method for keeping track of idle agents and for identifying which agent is the longest idle agent. In such systems, when an agent is servicing a caller, the agent's line is marked as busy, and the agent becomes unavailable for other calls. Thus in the event another caller attempts to call the agent, the request is denied.
However, it is sometimes necessary for the agent to access a supervisor or an information source line and conference the supervisor's or information line with that of the customer. With the agent's line being marked as busy, this has not been able to be done in such systems.